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  • From http://hubblesite.org/newscenter/archive/releases/galaxy/spiral/2009/07/image/g/results/50/ The galaxy Messier 101 is a swirling spiral of stars, gas, and dust. Messier 101 is nearly twice as wide as our Milky Way galaxy. Spitzer's view, taken in infrared light, reveals the galaxy's delicate dust lanes as yellow-green filaments. Such dense dust clouds are where new stars can form. In this image, dust warmed by the light of hot, young stars glows red. The rest of the galaxy's hundreds of billions of stars are less prominent and form a blue haze. Astronomers can use infrared light to examine the dust clouds where stars are born.
  • This Hubble Space Telescope view of the core of one of the nearest globular star clusters, called NGC 6397, resembles a treasure chest of glittering jewels. The cluster is located 8,200 light-years away in the constellation Ara. Here, the stars are jam-packed together. The stellar density is about a million times greater than in our Sun's stellar neighborhood. The stars are only a few light-weeks apart, while the nearest star to our Sun is over four light-years away. The stars in NGC 6397 are in constant motion, like a swarm of angry bees. The ancient stars are so crowded together that a few of them inevitably collide with each other once in a while. Near misses are even more common. Even so, collisions only occur every few million years or so. That's thousands of collisions in the 14-billion-year lifetime of the cluster. These Hubble images were taken for a research program aimed at studying what is left behind when such collisions and near misses occur. When direct collisions occur, the two stars may merge to form a new star called a "blue straggler"; these hot, bright, young stars stand out among the old stars that make up the vast majority of stars in a globular cluster. Several such bright blue stars are visible near the center of the cluster in the Hubble Heritage image. If two stars come close enough together without actually colliding, they may "capture" each other and become gravitationally bound. One type of binary that might form this way is a "cataclysmic variable"— a pairing of a normal, hydrogen-burning star and a burned-out star called a white dwarf. In a binary system, the white dwarf will pull material off the surface of the normal star. This material encircles the white dwarf in an "accretion disk," and eventually falls onto it. The result of this accretion process is that cataclysmic variables are, as the name suggests, variable in brightness. The heat generated by the accreting material also generates unusual amounts of ultraviolet and blue light. To search for cataclysmic variables, the program consisted of a series of 55 images of the cluster taken over a period of about 20 hours. Most of the images were taken in ultraviolet and blue filters; a few images were also taken at green and infrared wavelengths. By comparing the brightness of all the stars in all the images, the Hubble astronomers were able to identify several cataclysmic variable stars in the cluster. Comparison of their brightness in the different filters confirmed that they were emitting copious amounts of ultraviolet light. A few of these stars can be seen in the Hubble Heritage image as faint blue or violet stars. One of the more intriguing results of this study was completely unexpected. Three faint blue stars can be seen near the center of the cluster — in the Hubble Heritage image they appear turquoise. These three stars don't vary in brightness at all, and were clearly not cataclysmic variables. These stars may be very-low-mass white dwarfs, formed in the cores of giant stars whose evolution is somehow interrupted before a full-fledged white dwarf has time to form. Such an interruption might occur as the result of a stellar collision or an interaction with a binary companion. When a giant star interacts with another star, it can lose its outer layers prematurely, compared to its normal evolution, exposing its hot, blue core. The end result will be a white dwarf of a smaller mass than would have otherwise ensued. In any case, these unusual stars are yet more evidence that the center of a dense globular cluster is a perilous place to reside. A large number of normal white dwarfs were also identified and studied. These stars appear throughout the cluster, since they form through normal stellar evolution processes and don't involve any stellar interactions, which occur predominantly near the cluster center. Nearly 100 such burned-out stars were identified in these images, the brightest of which can be seen here as faint blue stars.
  • From http://hubblesite.org/newscenter/archive/releases/star-cluster/globular/2007/18/full/results/50/ Astronomers have long thought that globular star clusters had a single "baby boom" of stars early in their lives and then settled into a quiet existence. New observations by NASA's Hubble Space Telescope, however, are showing that this idea may be too simple. The Hubble analysis of the massive globular cluster NGC 2808 provides evidence that star birth went "boom, boom, boom," with three generations of stars forming very early in the cluster's life. "We had never imagined that anything like this could happen," said Giampaolo Piotto of the University of Padova in Italy and leader of the team that made the discovery. "This is a complete shock." Globular clusters are the homesteaders of our Milky Way Galaxy, born during our galaxy's formation. They are compact swarms of typically hundreds of thousands of stars held together by gravity. "The standard picture of a globular cluster is that all of its stars formed at the same time, in the same place, and from the same material, and they have co-evolved for billions of years," said team member Luigi Bedin of the European Space Agency, the European Organization for Astronomical Research in the Southern Hemisphere (ESO), in Garching, Germany, and the Space Telescope Science Institute in Baltimore, Md. "This is the cornerstone on which much of the study of stellar populations has been built. So we were very surprised to find several distinct populations of stars in NGC 2808. All of the stars were born within 200 million years very early in the life of the 12.5-billion-year-old massive cluster." Finding multiple stellar populations in a globular cluster so close to home has deep cosmological implications, the researchers said. "We need to do our best to solve the enigma of these multiple generations of stars found in these Hubble observations so that we can understand how stars formed in distant galaxies in our early universe," Piotto explained. The astronomers used Hubble's Advanced Camera for Surveys to measure the brightness and color of the cluster stars. Hubble's exquisite resolution allowed the astronomers to sort out the different stellar populations. The Hubble measurements showed three distinct populations, with each successive generation appearing slightly bluer. This color difference suggests that successive generations contain a slightly different mix of some chemical elements. "One assumption, although we have no direct proof," said team member Ivan King of the University of Washington in Seattle, "is that the successively bluer color of the stellar populations indicates that the amount of helium increases with each generation of stars. Perhaps massive star clusters like NGC 2808 hold onto enough gas to ignite a rapid succession of stars." The star birth would be driven by shock waves from supernovae and stellar winds from giant stars, which compress the gas and make new stars, King explained. The gas would be increasingly enriched in helium from previous generations of stars more massive than the Sun. Astronomers commonly assume that globular clusters produce only one stellar generation, because the energy radiating from the first batch of stars would clear out most of the residual gas needed to make more stars. But a hefty cluster like NGC 2808, which is two to three times more massive than a typical globular cluster, may have enough gravity to hang onto that gas, which has been enriched by helium from the first stars. Of the about 150 known globular clusters in our Milky Way Galaxy, NGC 2808 is one of the most massive, containing more than 1 million stars. Another possible explanation for the multiple stellar populations is that NGC 2808 may only be masquerading as a globular cluster. The stellar grouping may have been a dwarf galaxy that was stripped of most of its material due to gravitational capture by our galaxy. Omega Centauri, the only other stellar system Piotto's group found to have multiple generations of stars, is suspected to be the remnant core of a dwarf galaxy, Bedin said. Although the astronomers' search is only in its infancy, they say multiple stellar populations may be a typical occurrence in other massive clusters. "No one would make the radical step of suggesting that previous work on other clusters is no longer valid," King said. "But this discovery shows that the study of stellar populations in globular clusters now opens up in a new direction."
  • From http://hubblesite.org/newscenter/archive/releases/star-cluster/open/2004/20/text/results/50/ Astronomers using NASA's Hubble Space Telescope have helped settle a mystery that has puzzled scientists concerning the exact distance to the famous nearby star cluster known as the Pleiades, or the Seven Sisters. The Pleiades cluster, named by the ancient Greeks, is easily seen as a small grouping of stars lying near the shoulder of Taurus, the Bull, in the winter sky. Although it might be expected that the distance to this well-studied cluster would be well established, there has been an ongoing controversy among astronomers about its distance for the past seven years. The mystery began in 1997, when the European Space Agency's satellite Hipparcos measured the distance to the Pleiades and found it is 10 percent closer to Earth than traditional estimates, which were based on comparing the Pleiades to nearby stars. If the Hipparcos measurements were correct, then the stars in the Pleiades are peculiar because they are fainter than Sun-like stars would be at that distance. This finding, if substantiated, would challenge our basic understanding of the structure of stars. But measurements made by the Hubble telescope's Fine Guidance Sensors show that the distance to the Pleiades is about 440 light-years from Earth, essentially the same as past distance estimates and differing from the Hipparcos results by more than 40 light-years. The Hubble results will be presented June 1 at the American Astronomical Society meeting in Denver, Colo. The new results agree with recent measurements made by astronomers at the California Institute of Technology and NASA's Jet Propulsion Laboratory, both in Pasadena, Calif. Those astronomers used interferometer measurements from Mt. Wilson and Palomar observatories in California, reporting that the star cluster is between 434 and 446 light-years from Earth. The discrepancy in the distance to the Pleiades is more than an arcane argument over details. Astronomers have only one direct means for gauging distances to stars, called the parallax method. With current telescopes, this method gives accurate results only for distances up to about 500 light-years. Distances beyond that limit must be determined by indirect methods, based on comparing the brightness of distant stars with those of nearer ones of the same type, and making the assumption that both objects have the same intrinsic, or true, brightness. Astronomers can thus build up a distance ladder, based on ever more-distant objects, ultimately leading to the use of supernovae as "standard candles" for the most distant reaches of the universe. "Reliance on the accuracy of the measurements of nearby objects is crucial to getting the distance ladder of the universe correct," said David Soderblom of the Space Telescope Science Institute in Baltimore, Md., and lead astronomer on the Hubble study. "The new Hubble result shows that the measurements made by Hipparcos contain a small, but significant, source of error that requires further exploration. New space missions are now being planned to carry out even more precise distance measurements out to greater distances." Soderblom and his team used Hubble's Fine Guidance Sensors to measure slight changes in the apparent positions of three stars within the cluster when viewed from different sides of Earth's orbit. Due to the motion of the Earth around the Sun, the position of a star in the Pleiades, will appear to shift relative to stars farther away. This effect, called parallax, can be used to calculate the distance to the star with simple geometry; a similar method of triangulation is used by surveyors to measure distances on Earth. Soderblom's team took its measurements six months apart over a 2 1/2-year period. Making these kinds of measurements of a star's movement is very difficult. The Fine Guidance Sensors are so precise that if the human eye had the same ability to measure small angles, it would be able to see a quarter 16,000 miles away. Hipparcos was the first space observatory to make precise measurements of the positions and motions of celestial objects. Before Hipparcos, astronomers determined the distances to stars like the Pleiades by measuring parallax with ground-based telescopes. Those observations were less precise because Earth's atmosphere distorts light from stars, limiting the telescopes' resolution.
  • From http://hubblesite.org/newscenter/archive/releases/star%20cluster/open/2006/17/image/a/results/50/ NASA's Hubble Space Telescope has captured the most detailed images to date of the open star clusters NGC 265 and NGC 290 in the Small Magellanic Cloud — two sparkling sets of gemstones in the southern sky. These images, taken with Hubble's Advanced Camera for Surveys, show a myriad of stars in crystal clear detail. The brilliant open star clusters are located about 200,000 light-years away and are roughly 65 light-years across. Star clusters can be held together tightly by gravity, as is the case with densely packed crowds of hundreds of thousands of stars, called globular clusters. Or, they can be more loosely bound, irregularly shaped groupings of up to several thousands of stars, like the open clusters shown in this image. The stars in these open clusters are all relatively young and were born from the same cloud of interstellar gas. Just as old school-friends drift apart after graduation, the stars in an open cluster will only remain together for a limited time and gradually disperse into space, pulled away by the gravitational tugs of other passing clusters and clouds of gas. Most open clusters dissolve within a few hundred million years, whereas the more tightly bound globular clusters can exist for many billions of years. Open star clusters make excellent astronomical laboratories. The stars may have different masses, but all are at about the same distance, move in the same general direction, and have approximately the same age and chemical composition. They can be studied and compared to find out more about stellar evolution, the ages of such clusters, and much more. The Small Magellanic Cloud, which hosts the two star clusters, is one of the small satellite galaxies of the Milky Way. It can be seen with the unaided eye as a hazy patch in the constellation Tucana (the Toucan) in the Southern Hemisphere. The Small Magellanic Cloud is rich in gas nebulae and star clusters. It is most likely that this irregular galaxy has been disrupted through repeated interactions with the Milky Way, resulting in the vigorous star-forming activity seen throughout the cloud. NGC 265 and NGC 290 may very well owe their existence to these close encounters with the Milky Way. The images were taken in October and November 2004 through F435W, F555W, and F814W filters (shown in blue, green, and red, respectively).
  • From http://hubblesite.org/newscenter/archive/releases/star%20cluster/globular/1999/26/image/a/results/50/ This stellar swarm is M80 (NGC 6093), one of the densest of the 147 known globular star clusters in the Milky Way galaxy. Located about 28,000 light-years from Earth, M80 contains hundreds of thousands of stars, all held together by their mutual gravitational attraction. Globular clusters are particularly useful for studying stellar evolution, since all of the stars in the cluster have the same age (about 15 billion years), but cover a range of stellar masses. Every star visible in this image is either more highly evolved than, or in a few rare cases more massive than, our own Sun. Especially obvious are the bright red giants, which are stars similar to the Sun in mass that are nearing the ends of their lives. By analyzing the Wide Field and Planetary Camera 2 (WFPC2) images, including images taken through an ultraviolet filter, astronomers have found a large population of "blue stragglers" in the core of the cluster. These stars appear to be unusually young and more massive than the other stars in a globular cluster. However, stellar collisions can occur in dense stellar regions like the core of M80 and, in some cases, the collisions can result in the merger of two stars. This produces an unusually massive single star, which mimics a normal, young star. M80 was previously unknown to contain blue stragglers, but is now known to contain more than twice as many as any other globular cluster surveyed with NASA's Hubble Space Telescope (HST). Based on the number of blue stragglers, the stellar collision rate in the core of M80 appears to be exceptionally high. M80 is also unusual because it was the site of a nova explosion in the year 1860. Nova outbursts occur when a close companion star transfers fresh hydrogen fuel to a burned-out white dwarf. Eventually the hydrogen ignites a thermonuclear explosion on the surface of the white dwarf, giving rise to the nova outburst. The ultraviolet Hubble observations have revealed the hot, faint remnant of this exploding star, which was named T Scorpii in the 19th century. Curiously, however, the WFPC2 observations have revealed only two other nova-like close binary stars in M80, far fewer than expected theoretically based on the stellar collision rate. So the blue stragglers in M80 seem to indicate that there are lots of collisions, yet the nova-like stars suggest only a few. Sometimes life for astronomers isn't so simple, but it is from exploring discrepancies like this that our understanding eventually deepens.
  • Rising from a sea of dust and gas like a giant seahorse, the Horsehead nebula is one of the most photographed objects in the sky. The Hubble telescope took a close-up look at this heavenly icon, revealing the cloud's intricate structure. This detailed view of the horse's head is being released to celebrate the orbiting observatory's eleventh anniversary. 1. WHAT DOES THE PICTURE SHOW? The Horsehead is a cold, dark cloud of gas and dust, silhouetted against the bright nebula, IC 434. The top of the nebula also is being sculpted by radiation from a massive star located out of Hubble's field of view.
  • Information at http://hubblesite.org/newscenter/archive/releases/galaxy/spiral/2007/41/results/50/ NOVEMBER 29, 2007: Resembling festive lights on a holiday wreath, this NASA/ESA Hubble Space Telescope image of the nearby spiral galaxy M74 is an iconic reminder of the impending season. Bright knots of glowing gas light up the spiral arms, indicating a rich environment of star formation. M74 is located roughly 32 million light-years away in the direction of the constellation Pisces, the Fish. The image is a composite of Advanced Camera for Surveys data taken in 2003 and 2005.
  • Located in the constellation of Andromeda, the Princess, the Andromeda Galaxy is a large spiral galaxy very similar to our own Galaxy, the Milky Way. It is over 65,000 light-years in diameter and approximately 2.2 million light-years in distance. The area shown in this image is quite large on the sky, covering about five times the area of the full Moon.
  • Information on the galaxy on the left at http://hubblesite.org/newscenter/archive/releases/galaxy/elliptical/2007/08/image/a/results/50/ This image from NASA's Hubble Space Telescope shows the diverse collection of galaxies in the cluster Abell S0740 that is over 450 million light-years away in the direction of the constellation Centaurus. The giant elliptical ESO 325-G004 looms large at the cluster's center. The galaxy is as massive as 100 billion of our suns. Hubble resolves thousands of globular star clusters orbiting ESO 325-G004. Globular clusters are compact groups of hundreds of thousands of stars that are gravitationally bound together. At the galaxy's distance they appear as pinpoints of light contained within the diffuse halo. Other fuzzy elliptical galaxies dot the image. Some have evidence of a disk or ring structure that gives them a bow-tie shape. Several spiral galaxies are also present. The starlight in these galaxies is mainly contained in a disk and follows along spiral arms. This image was created by combining Hubble science observations taken in January 2005 with Hubble Heritage observations taken a year later to form a 3-color composite. The filters that isolate blue, red and infrared light were used with the Advanced Camera for Surveys aboard Hubble. Information on the galaxy on the right at http://hubblesite.org/newscenter/archive/releases/galaxy/elliptical/1995/07/results/50/ JUNE 14, 1995: This Hubble telescope photo mosaic shows a field of distant galaxies. The brightest object in this picture is NGC 4881 [just above center], an elliptical galaxy in the outskirts of the Coma Cluster, a great cluster of galaxies more than five times farther away than the Virgo Cluster. The distance to the Coma Cluster is an important cosmic yardstick for scaling the overall size of the universe.
  • About Image on Left: MARCH 3, 2005: What happens when a galaxy falls in with the wrong crowd? The irregular galaxy NGC 1427A is a spectacular example of the resulting stellar rumble. Under the gravitational grasp of a large gang of galaxies, called the Fornax cluster, the small bluish galaxy is plunging headlong into the group at 600 kilometers per second or nearly 400 miles per second. 1. IS NGC 1427A ACTIVELY FORMING STARS? NGC 1427A shows numerous hot, blue stars that have been formed very recently, showing that star formation is occurring extensively throughout the galaxy. Within the Fornax cluster, there is a considerable amount of gas lying between the galaxies. When the gas within NGC 1427A collides with the Fornax gas, it is compressed to the point that it starts to collapse under its own gravity. This leads to formation of the myriad of new stars seen across NGC 1427A. The tidal forces of nearby galaxies in the cluster may also play a role in triggering star formation on such a massive scale. 2. WHAT IS THE EVENTUAL FATE FOR NGC 1427A? NGC 1427A will not survive long as an identifiable galaxy passing through the cluster. Within the next billion years, it will be completely disrupted, spilling its stars and remaining gas into intergalactic space within the Fornax cluster. About image on right, From http://www.noao.edu/image_gallery/html/im0993.html The glowing gas of the interstellar medium (ISM) is the breeding ground for the formation of new stars, and the cemetery where the ashes of dead stars ultimately return. A team led by astronomers from the National Optical Astronomy Observatory (NOAO) has conducted a new study called the Magellanic Cloud Emission Line Survey (MCELS) that focused expressly on the ISM in the Large Magellanic Cloud and Small Magellanic Cloud—the nearest major galaxies to the Milky Way.
  • From http://news.nationalgeographic.com/news/2008/06/080603-milky-way.html Astronomers unveiled today what they are calling the best map ever produced of the Milky Way galaxy. The new view shows our spiral galaxy as it would look face-on to a very distant observer. The map is based on findings about the structural evolution of the Milky Way. The researchers determined that the Milky Way actually has two fewer major arms than previously believed. In barred spiral galaxies like our own, major arms have a high density of stars , produce lots of new stars, and are clearly connected to the long bar of stars at the galactic center. By contrast, minor arms have high gas density and presumably less star formation. Scientists had long thought that the Milky Way has four major arms. But the new images show that the spirals are actually made of two major arms and two minor ones. "These major arms plus the bar could be the things that really stand out if you were looking at the Milky Way galaxy from, say, [our nearest galactic neighbor] Andromeda," Benjamin said.
  • More information is at http://www.astronomynotes.com/starprop/s2.htm
  • http://starchild.gsfc.nasa.gov/docs/StarChild/questions/question19.html
  • http://coolcosmos.ipac.caltech.edu/cosmic_classroom/ir_tutorial/what_is_ir.html
  • From http://imagine.gsfc.nasa.gov/docs/science/how_l1/spectra.html Each element in the periodic table can appear in gaseous form and will produce a series of bright lines unique to that element. Hydrogen will not look like helium which will not look like carbon which will not look like iron... and so on. Thus, astronomers can identify what kinds of stuff are in stars from the lines they find in the star's spectrum. This type of study is called spectroscopy . The science of spectroscopy is quite sophisticated. From spectral lines astronomers can determine not only the element, but the temperature and density of that element in the star. The spectral line also can tell us about any magnetic field of the star. The width of the line can tell us how fast the material is moving. We can learn about winds in stars from this. If the lines shift back and forth we can learn that the star may be orbiting another star. We can estimate the mass and size of the star from this. If the lines grow and fade in strength we can learn about the physical changes in the star. Spectroscopy is one of the fundamental tools which scientists use to study the Universe.
  • Some information at http://antwrp.gsfc.nasa.gov/apod/ap000815.html Image and info at http://csep10.phys.utk.edu/astr162/lect/sun/spectrum.html or http://imagine.gsfc.nasa.gov/docs/teachers/gammaraybursts/imagine/page18.html
  • Explanation: Astronomers divide stars into different spectral types . First started in the 1800s, the spectral type was originally meant to classify the strength of hydrogen absorption lines . A few types that best describe the temperature of the star remain in use today. The seven main spectral types OBAFGKM are shown above with the spectrum of a single "O" star at the top followed by two spectra each from the progressively cooler designations, respectively. Historically, these letters have been remembered with the mnemonic "Oh Be A Fine Girl/Guy Kiss Me." Frequent classroom contests , however, have come up with other more/less politically correct mnemonics such as "Oven Baked Apples From Grandpa's/Grandma's Kitchen. Mmmm." Our Sun has spectral type "G".
  • http://sunearthday.gsfc.nasa.gov/2009/TTT/65_surfacetemp.php Image left: The Hertzsprung-Russell diagram developed by 2 astronomers in 1912, plots some of the characteristics of a large number of stars. They plotted spectral class vs. luminosity (brightness) of a large sample of stars. Our Sun's luminosity is 3.9 x 1026 Joules/s. The plot spans a large range in luminosity from a fraction of our Sun's brightness (0.01 times) to (10,000 times) much greater the strength of our Sun. Stellar surface temperatures range from 3,500 degrees Kelvin (K) (5,840 Fahrenheit (F)) to 50,000 K (89540 F). Our Sun is a G star. Credit: NASA http://www.nasa.gov/centers/goddard/news/topstory/2007/spectrum_plants.html
  • This new image taken with NASA's Hubble Space Telescope depicts bright, blue, newly formed stars that are blowing a cavity in the center of a star-forming region in the Small Magellanic Cloud. At the heart of the star-forming region, lies star cluster NGC 602. The high-energy radiation blazing out from the hot young stars is sculpting the inner edge of the outer portions of the nebula, slowly eroding it away and eating into the material beyond. The diffuse outer reaches of the nebula prevent the energetic outflows from streaming away from the cluster. Ridges of dust and gaseous filaments are seen towards the northwest (in the upper-left part of the image) and towards the southeast (in the lower right-hand corner). Elephant trunk-like dust pillars point towards the hot blue stars and are tell-tale signs of their eroding effect. In this region it is possible with Hubble to trace how the star formation started at the center of the cluster and propagated outward, with the youngest stars still forming today along the dust ridges. The Small Magellanic Cloud, in the constellation Tucana, is roughly 200,000 light-years from the Earth. Its proximity to us makes it an exceptional laboratory to perform in-depth studies of star formation processes and their evolution in an environment slightly different from our own Milky Way. Dwarf galaxies such as the Small Magellanic Cloud, with significantly fewer stars compared to our own galaxy, are considered to be the primitive building blocks of larger galaxies. The study of star formation within this dwarf galaxy is particularly interesting to astronomers because its primitive nature means that it lacks a large percentage of the heavier elements that are forged in successive generations of stars through nuclear fusion.
  • In commemoration of NASA's Hubble Space Telescope completing its 100,000th orbit in its 18th year of exploration and discovery, scientists at the Space Telescope Science Institute in Baltimore, Md., have aimed Hubble to take a snapshot of a dazzling region of celestial birth and renewal. Hubble peered into a small portion of the nebula near the star cluster NGC 2074 (upper, left). The region is a firestorm of raw stellar creation, perhaps triggered by a nearby supernova explosion. It lies about 170,000 light-years away near the Tarantula nebula, one of the most active star-forming regions in our Local Group of galaxies. The three-dimensional-looking image reveals dramatic ridges and valleys of dust, serpent-head "pillars of creation," and gaseous filaments glowing fiercely under torrential ultraviolet radiation. The region is on the edge of a dark molecular cloud that is an incubator for the birth of new stars. The high-energy radiation blazing out from clusters of hot young stars already born in NGC 2074 is sculpting the wall of the nebula by slowly eroding it away. Another young cluster may be hidden beneath a circle of brilliant blue gas at center, bottom. In this approximately 100-light-year-wide fantasy-like landscape, dark towers of dust rise above a glowing wall of gases on the surface of the molecular cloud. The seahorse-shaped pillar at lower, right is approximately 20 light-years long, roughly four times the distance between our Sun and the nearest star, Alpha Centauri. The region is in the Large Magellanic Cloud (LMC), a satellite of our Milky Way galaxy. It is a fascinating laboratory for observing star-formation regions and their evolution. Dwarf galaxies like the LMC are considered to be the primitive building blocks of larger galaxies.
  • This dramatic image offers a peek inside a cavern of roiling dust and gas where thousands of stars are forming. The image, taken by the Advanced Camera for Surveys (ACS) aboard NASA's Hubble Space Telescope, represents the sharpest view ever taken of this region, called the Orion Nebula. More than 3,000 stars of various sizes appear in this image. Some of them have never been seen in visible light. These stars reside in a dramatic dust-and-gas landscape of plateaus, mountains, and valleys that are reminiscent of the Grand Canyon. The Orion Nebula is a picture book of star formation, from the massive, young stars that are shaping the nebula to the pillars of dense gas that may be the homes of budding stars. The bright central region is the home of the four heftiest stars in the nebula. The stars are called the Trapezium because they are arranged in a trapezoid pattern. Ultraviolet light unleashed by these stars is carving a cavity in the nebula and disrupting the growth of hundreds of smaller stars. Located near the Trapezium stars are stars still young enough to have disks of material encircling them. These disks are called protoplanetary disks or "proplyds" and are too small to see clearly in this image. The disks are the building blocks of solar systems. The bright glow at upper left is from M43, a small region being shaped by a massive, young star's ultraviolet light. Astronomers call the region a miniature Orion Nebula because only one star is sculpting the landscape. The Orion Nebula has four such stars. Next to M43 are dense, dark pillars of dust and gas that point toward the Trapezium. These pillars are resisting erosion from the Trapezium's intense ultraviolet light. The glowing region on the right reveals arcs and bubbles formed when stellar winds - streams of charged particles ejected from the Trapezium stars — collide with material. The faint red stars near the bottom are the myriad brown dwarfs that Hubble spied for the first time in the nebula in visible light. Sometimes called "failed stars," brown dwarfs are cool objects that are too small to be ordinary stars because they cannot sustain nuclear fusion in their cores the way our Sun does. The dark red column, below, left, shows an illuminated edge of the cavity wall. The Orion Nebula is 1,500 light-years away, the nearest star-forming region to Earth. Astronomers used 520 Hubble images, taken in five colors, to make this picture. They also added ground-based photos to fill out the nebula. The ACS mosaic covers approximately the apparent angular size of the full moon. The Orion observations were taken between 2004 and 2005.
  • Movie at http://www.stsci.edu/EPA/PR/95/44/M16.mpg Eerie, dramatic pictures from the Hubble telescope show newborn stars emerging from "eggs" — not the barnyard variety — but rather, dense, compact pockets of interstellar gas called evaporating gaseous globules (EGGs). Hubble found the "EGGs," appropriately enough, in the Eagle nebula, a nearby star-forming region 7,000 light-years from Earth in the constellation Serpens. These striking pictures resolve the EGGs at the tip of finger-like features protruding from monstrous columns of cold gas and dust in the Eagle Nebula (also called M16). The columns — dubbed "elephant trunks" — protrude from the wall of a vast cloud of molecular hydrogen, like stalagmites rising above the floor of a cavern. Inside the gaseous towers, which are light-years long, the interstellar gas is dense enough to collapse under its own weight, forming young stars that continue to grow as they accumulate more and more mass from their surroundings.
  • Information on Venus’ history at http://www.nineplanets.org/venus.html Information on Mars’ history at http://www.nineplanets.org/mars.html Details and animations at http://www.nasa.gov/centers/goddard/news/topstory/2005/0801frozenworlds.html A sun-like star grows into its red giant phase, increasing in size and luminosity. Energy in the form of heat can now reach a once-frozen and dead moon. The icy surface quickly melts into liquid water, filling in old craters with warmer seas. The stage is now set for the possible formation of new life. Details on solar constant at http://www-das.uwyo.edu/~geerts/cwx/notes/chap02/solar_constant.html
  • NOVEMBER 5, 1998: NGC 3132 is a striking example of a planetary nebula. This expanding cloud of gas surrounding a dying star is known to amateur astronomers in the Southern Hemisphere as the "Eight-Burst" or the "Southern Ring" Nebula. The name "planetary nebula" refers only to the round shape that many of these objects show when examined through a small telescope. In reality, these nebulae have little or nothing to do with planets, but are instead huge shells of gas ejected by stars as they near the ends of their lifetimes. NGC 3132 is nearly half a light year in diameter, and at a distance of about 2,000 light-years is one of the nearest known planetary nebulae. The gases are expanding away from the central star at a speed of 9 miles per second.
  • Glowing like a multi-faceted jewel, the planetary nebula IC 418 lies about 2,000 light-years from Earth in the direction of the constellation Lepus. This photograph is one of the latest from NASA's Hubble Space Telescope, obtained with the Wide Field Planetary Camera 2. A planetary nebula represents the final stage in the evolution of a star similar to our Sun. The star at the center of IC 418 was a red giant a few thousand years ago, but then ejected its outer layers into space to form the nebula, which has now expanded to a diameter of about 0.1 light-year. The stellar remnant at the center is the hot core of the red giant, from which ultraviolet radiation floods out into the surrounding gas, causing it to fluoresce. Over the next several thousand years, the nebula will gradually disperse into space, and then the star will cool and fade away for billions of years as a white dwarf. Our own Sun is expected to undergo a similar fate, but fortunately this will not occur until some 5 billion years from now. The Hubble image of IC 418 is shown in a false-color representation, based on Wide Field Planetary Camera 2 exposures taken in February and September, 1999 through filters that isolate light from various chemical elements. Red shows emission from ionized nitrogen (the coolest gas in the nebula, located furthest from the hot nucleus), green shows emission from hydrogen, and blue traces the emission from ionized oxygen (the hottest gas, closest to the central star). The remarkable textures seen in the nebula are newly revealed by the Hubble telescope, and their origin is still uncertain.
  • In this detailed view from NASA's Hubble Space Telescope, the so-called Cat's Eye Nebula looks like the penetrating eye of the disembodied sorcerer Sauron from the film adaptation of "The Lord of the Rings." The nebula, formally cataloged NGC 6543, is every bit as inscrutable as the J.R.R. Tolkien phantom character. Though the Cat's Eye Nebula was one of the first planetary nebulae to be discovered, it is one of the most complex such nebulae seen in space. A planetary nebula forms when Sun-like stars gently eject their outer gaseous layers that form bright nebulae with amazing and confounding shapes. In 1994, Hubble first revealed NGC 6543's surprisingly intricate structures, including concentric gas shells, jets of high-speed gas, and unusual shock-induced knots of gas. As if the Cat's Eye itself isn't spectacular enough, this new image taken with Hubble's Advanced Camera for Surveys (ACS) reveals the full beauty of a bull's eye pattern of eleven or even more concentric rings, or shells, around the Cat's Eye. Each 'ring' is actually the edge of a spherical bubble seen projected onto the sky — that's why it appears bright along its outer edge. Observations suggest the star ejected its mass in a series of pulses at 1,500-year intervals. These convulsions created dust shells, each of which contain as much mass as all of the planets in our solar system combined (still only one percent of the Sun's mass). These concentric shells make a layered, onion-skin structure around the dying star. The view from Hubble is like seeing an onion cut in half, where each skin layer is discernible. Until recently, it was thought that such shells around planetary nebulae were a rare phenomenon. However, Romano Corradi (Isaac Newton Group of Telescopes, Spain) and collaborators, in a paper published in the European journal Astronomy and Astrophysics in April 2004, have instead shown that the formation of these rings is likely to be the rule rather than the exception. The bull's-eye patterns seen around planetary nebulae come as a surprise to astronomers because they had no expectation that episodes of mass loss at the end of stellar lives would repeat every 1,500 years. Several explanations have been proposed, including cycles of magnetic activity somewhat similar to our own Sun's sunspot cycle, the action of companion stars orbiting around the dying star, and stellar pulsations. Another school of thought is that the material is ejected smoothly from the star, and the rings are created later on due to formation of waves in the outflowing material. It will take further observations and more theoretical studies to decide between these and other possible explanations. Approximately 1,000 years ago the pattern of mass loss suddenly changed, and the Cat's Eye Nebula started forming inside the dusty shells. It has been expanding ever since, as discernible in comparing Hubble images taken in 1994, 1997, 2000, and 2002. The puzzle is what caused this dramatic change? Many aspects of the process that leads a star to lose its gaseous envelope are still poorly known, and the study of planetary nebulae is one of the few ways to recover information about these last few thousand years in the life of a Sun-like star.
  • From http://hubblesite.org/newscenter/archive/releases/nebula/emission/1997/33/results/50/ Astronomers using the Hubble telescope have identified what may be the most luminous star known ? a celestial mammoth that releases up to 10 million times the power of the Sun and is big enough to fill the diameter of Earth's orbit. The star [center of image] unleashes as much energy in six seconds as our Sun does in one year. The image, taken in infrared light, also reveals a bright nebula [magenta-colored material], created by extremely massive stellar eruptions. The nebula is so big (4 light-years) that it would nearly span the distance from the Sun to Alpha Centauri, the nearest star to Earth's solar system.
  • This is the first direct image of a star other than the Sun, made with NASA's Hubble Space Telescope. Called Alpha Orionis, or Betelgeuse, it is a red supergiant star marking the shoulder of the winter constellation Orion the Hunter (diagram at right). The Hubble image reveals a huge ultraviolet atmosphere with a mysterious hot spot on the stellar behemoth's surface. The enormous bright spot, twice the diameter of the Earth's orbit, is at least 2,000 Kelvin degrees hotter than the surface of the star. The image suggests that a totally new physical phenomenon may be affecting the atmospheres of some stars. Follow-up observations will be needed to help astronomers understand whether the spot is linked to oscillations previously detected in the giant star, or whether it moves systematically across the star's surface under the grip of powerful magnetic fields. The observations were made by Andrea Dupree of the Harvard- Smithsonian Center for Astrophysics in Cambridge, MA, and Ronald Gilliland of the Space Telescope Science Institute in Baltimore, MD, who announced their discovery today at the 187th meeting of the American Astronomical Society in San Antonio, Texas. The image was taken in ultraviolet light with the Faint Object Camera on March 3, 1995. Hubble can resolve the star even though the apparent size is 20,000 times smaller than the width of the full Moon — roughly equivalent to being able to resolve a car's headlights at a distance of 6,000 miles. Betelgeuse is so huge that, if it replaced the Sun at the center of our Solar System, its outer atmosphere would extend past the orbit of Jupiter (scale at lower left).
  • (top right) FEBRUARY 19, 2004: Seventeen years ago, astronomers spotted the brightest stellar explosion ever seen since the one observed by Johannes Kepler 400 years ago. Called SN 1987A, the titanic supernova explosion blazed with the power of 100,000,000 suns for several months following its discovery on Feb. 23, 1987. Although the supernova itself is a million times fainter than 17 years ago, a new light show in the space surrounding it is just beginning. This image, taken Nov. 28, 2003 by the Advanced Camera for Surveys aboard NASA's Hubble Space Telescope, shows many bright spots along a ring of gas, like pearls on a necklace. These cosmic "pearls" are being produced as a supersonic shock wave unleashed during the explosion slams into the ring at more than a million miles per hour. The collision is heating the gas ring, causing its innermost regions to glow. Curiously, one of the bright spots on the ring [at 4 o'clock] is a star that happens to lie along the telescope's line of sight. Left: This new movie of X-ray data from Chandra of the supernova remnant Cassiopeia A (Cas A) was made by combining observations taken in January 2000, February 2002, February 2004, and December 2007. In these images, the lowest-energy X-rays Chandra detects are shown in red, intermediate energies in green, and the highest energies in blue. Scientists have used the movie to measure the expansion velocity of the leading edge of the explosion's outer blast wave (shown in blue). The researchers find that the velocity is 11 million miles per hour, which is significantly slower than expected for an explosion with the energy estimated to have been released in Cas A. This slower velocity is explained by a special type of energy loss by the blast wave. Electrons are accelerated to high energies as they travel backwards and forwards across the shock front produced by the blast wave. As the electrons travel around magnetic fields in the shock they lose energy by producing synchrotron emission and glowing in X-rays. Scientists think heavier particles like protons and ions are accelerated in the same way. The energy lost by these heavier particles can amount to a large fraction of the energy from the supernova explosion, resulting in a slower shock velocity. The accelerated protons and ions which escape from the remnant are known as " cosmic rays ", and continually bombard the Earth's atmosphere. Supernova remnants are believed to be one of the main sources of cosmic rays. The authors have constructed a model that combined the measured expansion velocity, as well as its observed size, with estimates of the explosion energy, the mass of the ejected material in Cas A and efficient particle acceleration. For everything to agree, about 35% of the energy of the Cas A supernova went into accelerating cosmic rays. Another new feature seen in the Cas A movie is "flickering" of the blue synchrotron emission seen on timescales of about a year. This flickering is thought to be a direct result of acceleration of particles to high energies, causing the emission to become brighter, followed by rapid cooling, causing the emission to fade. These variations provide important clues about the location of the acceleration, a topic of some controversy. For the first time, this flaring is seen in the outer blast wave. This casts doubt upon the possibility, suggested previously, that cosmic ray acceleration occurs in the so-called " reverse shock ". This is a shock that travels backwards into the expanding remnant and is therefore located inside the outer blast wave. Previous claims that flaring occurs in the reverse shock may simply have been caused by regions in the outer blast wave that are projected onto the middle of the two-dimensional image. The rapid flickering not only gives information about acceleration of particles to high energies, but it also shows that relatively strong magnetic fields have been generated in the shock front. The Crab Nebula (bottom right) is a six-light-year-wide expanding remnant of a star's supernova explosion. Japanese and Chinese astronomers recorded this violent event nearly 1,000 years ago in 1054, as did, almost certainly, Native Americans. This composite image was assembled from 24 individual exposures taken with the NASA Hubble Space Telescope’s Wide Field and Planetary Camera 2 in October 1999, January 2000, and December 2000. It is one of the largest images taken by Hubble and is the highest resolution image ever made of the entire Crab Nebula.
  • GRO J1655-40 is the second so-called 'microquasar' discovered in our Galaxy. Microquasars are black holes of about the same mass as a star. They behave as scaled-down versions of much more massive black holes that are at the cores of extremely active galaxies, called quasars. Astronomers have known about the existence of stellar-mass black holes since the early 1970s. Their masses can range from 3.5 to approximately 15 times the mass of our Sun. Using Hubble data, astronomers were able to describe the black-hole system. The companion star had apparently survived the original supernova explosion that created the black hole. It is an aging star that completes an orbit around the black hole every 2.6 days. It is being slowly devoured by the black hole. Blowtorch-like jets (shown in blue) are streaming away from the black-hole system at 90 percent of the speed of light.
  • From http://hubblesite.org/newscenter/archive/releases/galaxy/spiral/2005/01/results/50/ WHAT IS A BARRED SPIRAL GALAXY? Barred spirals differ from normal spiral galaxies in that the arms of the galaxy do not spiral all the way into the center, but are connected to the two ends of a straight bar of stars containing the nucleus at its center. NGC 1300 is considered to be prototypical of barred spiral galaxies. 2. HOW DOES THE NUCLEUS OF NGC 1300 LOOK DIFFERENT FROM OTHER SPIRAL GALAXIES? In the core of the larger spiral structure of NGC 1300, the nucleus shows its own extraordinary and distinct "grand-design" spiral structure that is about 3,300 light-years long. Only galaxies with large-scale bars appear to have these grand-design inner disks — a spiral within a spiral. Models suggest that the gas in a bar can be funneled inwards, and then spiral into the center through the grand-design disk, where it can potentially fuel a central black hole. NGC 1300 is not known to have an active nucleus, however, indicating either that there is no black hole, or that it is not accreting matter.
  • Located in the constellation of Andromeda, the Princess, the Andromeda Galaxy is a large spiral galaxy very similar to our own Galaxy, the Milky Way. It is over 65,000 light-years in diameter and approximately 2.2 million light-years in distance. The area shown in this image is quite large on the sky, covering about five times the area of the full Moon.
  • Information at http://hubblesite.org/newscenter/archive/releases/galaxy/spiral/2006/24/image/a/results/50/ This is a unique NASA Hubble Space Telescope view of the disk galaxy NGC 5866 tilted nearly edge-on to our line-of-sight. Hubble's sharp vision reveals a crisp dust lane dividing the galaxy into two halves. The image highlights the galaxy's structure: a subtle, reddish bulge surrounding a bright nucleus, a blue disk of stars running parallel to the dust lane, and a transparent outer halo. Some faint, wispy trails of dust can be seen meandering away from the disk of the galaxy out into the bulge and inner halo of the galaxy. The outer halo is dotted with numerous gravitationally bound clusters of nearly a million stars each, known as globular clusters. Background galaxies that are millions to billions of light-years farther away than NGC 5866 are also seen through the halo. NGC 5866 is a disk galaxy of type "S0" (pronounced s-zero). Viewed face on, it would look like a smooth, flat disk with little spiral structure. It remains in the spiral category because of the flatness of the main disk of stars as opposed to the more spherically rotund (or ellipsoidal) class of galaxies called "ellipticals." Such S0 galaxies, with disks like spirals and large bulges like ellipticals, are called 'lenticular' galaxies. The dust lane is slightly warped compared to the disk of starlight. This warp indicates that NGC 5866 may have undergone a gravitational tidal disturbance in the distant past, by a close encounter with another galaxy. This is plausible because it is the largest member of a small cluster known as the NGC 5866 group of galaxies. The starlight disk in NGC 5866 extends well beyond the dust disk. This means that dust and gas still in the galaxy and potentially available to form stars does not stretch nearly as far out in the disk as it did when most of these stars in the disk were formed. The Hubble image shows that NGC 5866 shares another property with the more gas-rich spiral galaxies. Numerous filaments that reach out perpendicular to the disk punctuate the edges of the dust lane. These are short-lived on an astronomical scale, since clouds of dust and gas will lose energy to collisions among themselves and collapse to a thin, flat disk. For spiral galaxies, the incidence of these fingers of dust correlates well with indicators of how many stars have been formed recently, as the input of energy from young massive stars moves gas and dust around to create these structures. The thinness of dust lanes in S0s has been discussed in ground-based galaxy atlases, but it took the resolution of Hubble to show that they can have their own smaller fingers and chimneys of dust. NGC 5866 lies in the Northern constellation Draco, at a distance of 44 million light-years (13.5 Megaparsecs). It has a diameter of roughly 60,000 light-years (18,400 parsecs) only two-thirds the diameter of the Milky Way, although its mass is similar to our galaxy. This Hubble image of NGC 5866 is a combination of blue, green and red observations taken with the Advanced Camera for Surveys in November 2005.
  • Information on the galaxy on the left at http://hubblesite.org/newscenter/archive/releases/galaxy/elliptical/2007/08/image/a/results/50/ This image from NASA's Hubble Space Telescope shows the diverse collection of galaxies in the cluster Abell S0740 that is over 450 million light-years away in the direction of the constellation Centaurus. The giant elliptical ESO 325-G004 looms large at the cluster's center. The galaxy is as massive as 100 billion of our suns. Hubble resolves thousands of globular star clusters orbiting ESO 325-G004. Globular clusters are compact groups of hundreds of thousands of stars that are gravitationally bound together. At the galaxy's distance they appear as pinpoints of light contained within the diffuse halo. Other fuzzy elliptical galaxies dot the image. Some have evidence of a disk or ring structure that gives them a bow-tie shape. Several spiral galaxies are also present. The starlight in these galaxies is mainly contained in a disk and follows along spiral arms. This image was created by combining Hubble science observations taken in January 2005 with Hubble Heritage observations taken a year later to form a 3-color composite. The filters that isolate blue, red and infrared light were used with the Advanced Camera for Surveys aboard Hubble. Information on the galaxy on the right at http://hubblesite.org/newscenter/archive/releases/galaxy/elliptical/1995/07/results/50/ JUNE 14, 1995: This Hubble telescope photo mosaic shows a field of distant galaxies. The brightest object in this picture is NGC 4881 [just above center], an elliptical galaxy in the outskirts of the Coma Cluster, a great cluster of galaxies more than five times farther away than the Virgo Cluster. The distance to the Coma Cluster is an important cosmic yardstick for scaling the overall size of the universe.
  • From Tightly wound, almost concentric, arms of dark dust encircle the bright nucleus of the galaxy NGC 2787 in this Hubble Space Telescope image. In astronomer Edwin Hubble's galaxy classification scheme, NGC 2787 is classified as an SB0, a barred lenticular galaxy. These lens-shaped galaxies show little or no evidence of the grand spiral arms that occur in their more photogenic cousins, though NGC 2787 does sport a faint bar, not apparent in this image. The picture was created by the Hubble Heritage team.
  • About Image on Left: MARCH 3, 2005: What happens when a galaxy falls in with the wrong crowd? The irregular galaxy NGC 1427A is a spectacular example of the resulting stellar rumble. Under the gravitational grasp of a large gang of galaxies, called the Fornax cluster, the small bluish galaxy is plunging headlong into the group at 600 kilometers per second or nearly 400 miles per second. 1. IS NGC 1427A ACTIVELY FORMING STARS? NGC 1427A shows numerous hot, blue stars that have been formed very recently, showing that star formation is occurring extensively throughout the galaxy. Within the Fornax cluster, there is a considerable amount of gas lying between the galaxies. When the gas within NGC 1427A collides with the Fornax gas, it is compressed to the point that it starts to collapse under its own gravity. This leads to formation of the myriad of new stars seen across NGC 1427A. The tidal forces of nearby galaxies in the cluster may also play a role in triggering star formation on such a massive scale. 2. WHAT IS THE EVENTUAL FATE FOR NGC 1427A? NGC 1427A will not survive long as an identifiable galaxy passing through the cluster. Within the next billion years, it will be completely disrupted, spilling its stars and remaining gas into intergalactic space within the Fornax cluster. About image on right, From http://www.noao.edu/image_gallery/html/im0993.html The glowing gas of the interstellar medium (ISM) is the breeding ground for the formation of new stars, and the cemetery where the ashes of dead stars ultimately return. A team led by astronomers from the National Optical Astronomy Observatory (NOAO) has conducted a new study called the Magellanic Cloud Emission Line Survey (MCELS) that focused expressly on the ISM in the Large Magellanic Cloud and Small Magellanic Cloud—the nearest major galaxies to the Milky Way.
  • Information at http://hubblesite.org/newscenter/archive/releases/galaxy/interacting/2000/34/results/50/ What appears as a bird's head, leaning over to snatch up a tasty meal, is a striking example of a galaxy collision in NGC 6745. The "bird" is a large spiral galaxy, with its core still intact. It is peering at its "prey," a smaller passing galaxy (nearly out of the field of view at lower right). The bright blue beak and bright, whitish-blue top feathers show the distinct path taken during the smaller galaxy's journey. These galaxies did not merely interact gravitationally as they passed one another; they actually collided. Q & A: UNDERSTANDING THE DISCOVERY 1. WHAT HAPPENS WHEN GALAXIES COLLIDE? When galaxies collide, the stars that are part of each galaxy will almost never collide. They usually pass freely between each other with little damage. That's because the stars are far apart from each other. But the vast clouds of gas and dust between the stars do smash into each other. These collisions compress the clouds and trigger new star birth. The hot blue stars in this image are evidence of this star formation.
  • Information at http://hubblesite.org/newscenter/archive/releases/galaxy/interacting/1997/34/results/50/ The Hubble telescope has uncovered over 1,000 bright; young star clusters bursting to life in a brief, intense, brilliant "fireworks show" at the heart of a pair of colliding galaxies. The picture on the left provides a sweeping view of the two galaxies, called the Antennae. The green shape pinpoints Hubble's view. Hubble's close-up view [right] provides a detailed look at the "fireworks" at the center of this wreck. The respective cores of the twin galaxies are the orange blobs, left and right of center, crisscrossed by filaments of dark dust. A wide band of chaotic dust stretches between the cores of the two galaxies. The sweeping spiral-like patterns, traced by bright blue star clusters, are the result of a firestorm of star birth that was triggered by the collision.
  • Left Image: A nearly perfect ring of hot, blue stars pinwheels about the yellow nucleus of an unusual galaxy known as Hoag's Object. This image from NASA's Hubble Space Telescope captures a face-on view of the galaxy's ring of stars, revealing more detail than any existing photo of this object. The image may help astronomers unravel clues on how such strange objects form. The entire galaxy is about 120,000 light-years wide, which is slightly larger than our Milky Way Galaxy. The blue ring, which is dominated by clusters of young, massive stars, contrasts sharply with the yellow nucleus of mostly older stars. What appears to be a "gap" separating the two stellar populations may actually contain some star clusters that are almost too faint to see. Curiously, an object that bears an uncanny resemblance to Hoag's Object can be seen in the gap at the one o'clock position. The object is probably a background ring galaxy. Ring-shaped galaxies can form in several different ways. One possible scenario is through a collision with another galaxy. Sometimes the second galaxy speeds through the first, leaving a "splash" of star formation. But in Hoag's Object there is no sign of the second galaxy, which leads to the suspicion that the blue ring of stars may be the shredded remains of a galaxy that passed nearby. Some astronomers estimate that the encounter occurred about 2 to 3 billion years ago. This unusual galaxy was discovered in 1950 by astronomer Art Hoag. Hoag thought the smoke-ring-like object resembled a planetary nebula, the glowing remains of a Sun-like star. But he quickly discounted that possibility, suggesting that the mysterious object was most likely a galaxy. Observations in the 1970s confirmed this prediction, though many of the details of Hoag's galaxy remain a mystery. The galaxy is 600 million light-years away in the constellation Serpens. The Wide Field and Planetary Camera 2 took this image on July 9, 2001. Right image: Located about 130 million light-years away, NGC 4650A is one of only 100 known polar-ring galaxies. Their unusual disk-ring structure is not yet understood fully. One possibility is that polar rings are the remnants of colossal collisions between two galaxies sometime in the distant past, probably at least 1 billion years ago. What is left of one galaxy has become the rotating inner disk of old red stars in the center. Meanwhile, another smaller galaxy which ventured too close was probably severely damaged or destroyed. During the collision the gas from the smaller galaxy would have been stripped off and captured by the larger galaxy, forming a new ring of dust, gas, and stars, which orbit around the inner galaxy almost at right angles to the old disk.
  • Information at http://hubblesite.org/newscenter/archive/releases/galaxy/cluster/1999/31/results/50/ This troupe of four galaxies, known as Hickson Compact Group 87 (HCG 87), is performing an intricate dance orchestrated by the mutual gravitational forces acting between them. The dance is a slow, graceful minuet, occurring over a time span of hundreds of millions of years. This Hubble telescope image reveals complex details in the dust lanes of the group's largest galaxy member (HCG 87a), which is actually disk-shaped, but tilted so that we see it nearly edge-on. Both 87a and its elliptically shaped nearest neighbor (87b) have active galactic nuclei, which are believed to harbor black holes that are consuming gas. A third group member, the nearby spiral galaxy 87c, may be undergoing a burst of active star formation. The three galaxies are so close to each other that gravitational forces disrupt their structure and alter their evolution.
  • The Hubble telescope has taken a snapshot of a nearby active galaxy known as Circinus. This active galaxy belongs to a class of mostly spiral galaxies called Seyferts, which have compact centers and are believed to contain massive black holes. Seyfert galaxies are themselves part of a larger class of objects called Active Galactic Nuclei or AGN. AGN have the ability to remove gas from the centers of their galaxies by blowing it out into space at phenomenal speeds. Astronomers studying the Circinus galaxy are seeing evidence of a powerful AGN at its center.
  • Image on Left: Resembling a gigantic hubcap in space, a 3,700-light-year-wide dust disk encircles a 300-million- solar-mass black hole in the center of the elliptical galaxy NGC 7052. The disk, possibly a remnant of an ancient galaxy collision, will be swallowed up by the black hole in several billion years. The black-and-white image on the left, taken by a ground-based telescope, shows the complete galaxy. The Hubble picture on the right is a close-up view of the dust disk surrounding the black hole. Image on Right: A monstrous black hole's rude table manners include blowing huge bubbles of hot gas into space. At least, that's the gustatory practice followed by the supermassive black hole residing in the hub of the nearby galaxy NGC 4438. Known as a peculiar galaxy because of its unusual shape, NGC 4438 is in the Virgo Cluster, 50 million light-years from Earth. These NASA Hubble Space Telescope images of the galaxy's central region clearly show one of the bubbles rising from a dark band of dust. The other bubble, emanating from below the dust band, is barely visible, appearing as dim red blobs in the close-up picture of the galaxy's hub (the colorful picture at right). The background image represents a wider view of the galaxy, with the central region defined by the white box. These extremely hot bubbles are caused by the black hole's voracious eating habits. The eating machine is engorging itself with a banquet of material swirling around it in an accretion disk (the white region below the bright bubble). Some of this material is spewed from the disk in opposite directions. Acting like high-powered garden hoses, these twin jets of matter sweep out material in their paths. The jets eventually slam into a wall of dense, slow-moving gas, which is traveling at less than 223,000 mph (360,000 kph). The collision produces the glowing material. The bubbles will continue to expand and will eventually dissipate. Compared with the life of the galaxy, this bubble-blowing phase is a short-lived event. The bubble is much brighter on one side of the galaxy's center because the jet smashed into a denser amount of gas. The brighter bubble is 800 light-years tall and 800 light-years across.
  • NASA's Hubble Space Telescope captures the magnificent starry population of the Coma Cluster of galaxies, one of the densest known galaxy collections in the universe. The Hubble's Advanced Camera for Surveys viewed a large portion of the cluster, spanning several million light-years across. The entire cluster contains thousands of galaxies in a spherical shape more than 20 million light-years in diameter. Also known as Abell 1656, the Coma Cluster is over 300 million light-years away. The cluster, named after its parent constellation Coma Berenices, is near the Milky Way's north pole. This places the Coma Cluster in an area unobscured by dust and gas from the plane of the Milky Way, and easily visible by Earth viewers. Most of the galaxies that inhabit the central portion of the Coma Cluster are ellipticals. These featureless "fuzz-balls" are pale goldish brown in color and contain populations of old stars. Both dwarf, as well as giant ellipticals, are found in abundance in the Coma Cluster. Farther out from the center of the cluster are several spiral galaxies. These galaxies have clouds of cold gas that are giving birth to new stars. Spiral arms and dust lanes "accessorize" these bright bluish-white galaxies that show a distinctive disk structure. In between the ellipticals and spirals is a morphological class of objects known as S0 (S-zero) galaxies. They are made up of older stars and show little evidence of recent star formation; however, they do show some assemblage of structure — perhaps a bar or a ring, which may give rise to a more disk-like feature. This Hubble image consists of a section of the cluster that is roughly one-third of the way out from the center of the cluster. One bright spiral galaxy is visible in the upper left of the image. It is distinctly brighter and bluer than galaxies surrounding it. A series of dusty spiral arms appears reddish brown against the whiter disk of the galaxy, and suggests that this galaxy has been disturbed at some point in the past. The other galaxies in the image are either ellipticals, S0 galaxies, or background galaxies far beyond the Coma Cluster sphere. The data of the Coma Cluster were taken as part of a survey of a nearby rich galaxy cluster. Collectively they will provide a key database for studies of galaxy formation and evolution. This survey will also help to compare galaxies in different environments, both crowded and isolated, as well as to compare relatively nearby galaxies to more distant ones (at higher redshifts).
  • New evidence from NASA's Galaxy Evolution Explorer supports the long-held notion that many galaxies begin life as smaller spirals before transforming into larger, elliptical-shaped galaxies. Examples of young, teenage and adult galaxies are shown here from left to right. The data making up these photos come from both the Galaxy Evolution Explorer and visible-light telescopes. Long-wavelength ultraviolet light is blue; short-wavelength ultraviolet light is green; and visible red light is red. The galaxy on the left is NGC 300, a spiral located about seven million light-years away in the constellation Sculptor. Younger galaxies like this one tend to form more stars, and since new stars give off more ultraviolet and blue light, the galaxies appear blue. The galaxy on the right is NGC 1316, located about 62 million light-years away in the constellation Fornax. It is an older elliptical. Older stars emit more red light, so this galaxy appears red. The galaxies in the middle of the diagram represent the teenagers, which are on their way from becoming blue to red. The relatively small patches of ultraviolet light in these transitional galaxies indicate that star formation is winding down. The galaxy at center left is NGC 4569, located about four million light-years away in the constellation Virgo. The galaxy at center right is NGC 1291, located about 33 million light-years away in the constellation Eridanus. Before the Galaxy Evolution Explorer launched more than four years ago, there weren't a lot of examples of transitional galaxies, which made it difficult to demonstrate that galaxies mature from blue to red. The Galaxy Evolution Explorer allowed astronomers to find good examples of these elusive teenagers through its extensive catalogue of tens of thousands of galaxies photographed in ultraviolet light. Credit: NASA/JPL-Caltech/CTIO/Las Campanas/Palomar
  • Einstein’s theory of relativity predicts this “smaller than a proton” time=0 state
  • Light at 300,000 years
  • This artist's conception illustrates the decline in our universe's "birth-rate" over time. When the universe was young, massive galaxies were forming regularly, like baby bees in a bustling hive. In time, the universe bore fewer and fewer "offspring," and newborn galaxies (white circles) matured into older ones more like our own Milky Way (spirals). Previously, astronomers thought that the universe had ceased to give rise to massive, young galaxies, but findings from NASA's Galaxy Evolution Explorer suggest that may not be the case. Surveying thousands of nearby galaxies with its highly sensitive ultraviolet eyes, the telescope spotted three dozen that greatly resemble youthful galaxies from billions of years ago. In this illustration, those galaxies are represented as white circles on the right, or "today" side of the timeline. The discovery not only suggests that our universe may still be alive with youth, but also offers astronomers their first close-up look at what appear to be baby galaxies. Prior to the new result, astronomers had to peer about 11 billion light-years into the distant universe to see newborn galaxies. The newfound galaxies are only about 2 to 4 billion light-years away.
  • They used calculations to show that tiny impulse might cause entire universe to expand or contract Fred Hoyle coined term “Big Bang” – he believed in steady state universe based on general theory of relativity More information is available at http://map.gsfc.nasa.gov/universe/bb_theory.html
  • Good, but not exceptional high school student – a better athlete (broke Illinois State high jump record) Played college basketball
  • More information at http://map.gsfc.nasa.gov/universe/bb_tests.html
  • Shipp: Red shift - can determine composition of star, and relative movement by measuring its spectrum. Wavelengths shift toward red if moving away. Faster the velocity, more of a red shift. Wellner: wavelength shifts to the red end of the spectrum as Doppler Effect while light travels through universe (gravitational effect on photons) Hubble - universe is expanding (red shift) and things farther away are moving away faster (greater red shift) Differences in age b/c we don’t know the size of the universe. Doppler effect - shift in wavelength - light and sound Compressed as it approaches - higher pitched an shorter waved Stretched as it leaves - lower pitch, longer wave
  • Stars galaxies powerpoint

    1. 1. Stars and Galaxies Space Science for Middle School at HCDE February 20, 2009 Created by the Lunar and Planetary Institute For Educational Use Only LPI is not responsible for the ways in which this powerpoint may be used or altered. Image at http://hubblesite.org/newscenter/archive/releases/galaxy/spiral/2009/07/image/g/results/50/
    2. 2. Welcome! <ul><li>Please complete the pre-assessment </li></ul><ul><li>It’s for us—it’s not about you </li></ul><ul><li>Please let us know how much YOU know, not how much your friends sitting next to you know </li></ul>
    3. 3. What are we going to cover? <ul><li>Our Place in the Universe </li></ul><ul><li>The Electromagnetic Spectrum </li></ul><ul><li>Classifying Stars </li></ul><ul><li>Classifying Galaxies </li></ul><ul><li>History of the Universe </li></ul>
    4. 4. First up… <ul><li>Our Place in the Universe </li></ul><ul><ul><li>What is our Universe made of? </li></ul></ul><ul><ul><li>How big are things? How far away? </li></ul></ul><ul><ul><li>How do we know? </li></ul></ul>
    5. 5. What is our Universe made of? <ul><li>Stars and planets </li></ul><ul><li>Gas and dust </li></ul><ul><li>Organized into star clusters </li></ul><ul><li>Organized into nebulae </li></ul><ul><li>Organized into galaxies </li></ul><ul><li>Other things: </li></ul><ul><ul><li>Black holes </li></ul></ul><ul><ul><li>Dark matter </li></ul></ul><ul><ul><li>Dark energy </li></ul></ul>What was in your drawing? Image from http://galileo.rice.edu/lib/student_work/astronomy95/orionpleiades.html
    6. 6. Activity!! <ul><li>Use the Venn diagrams to place the stickers—where does everything go? </li></ul><ul><li>After you’re finished, let’s discuss… </li></ul>
    7. 7. Examining the Components <ul><li>Stars </li></ul><ul><li>Gas and dust (Nebulae) </li></ul><ul><li>Star clusters </li></ul><ul><li>Galaxies </li></ul>
    8. 8. Different types of stars Image from http://hubblesite.org/newscenter/archive/releases/star%20cluster/globular/2003/21/image/a/results/50/
    9. 9. Types of Stars <ul><li>Big </li></ul><ul><li>Small </li></ul><ul><li>Red </li></ul><ul><li>Blue </li></ul><ul><li>Yellow </li></ul><ul><li>In groups </li></ul><ul><li>Alone </li></ul><ul><ul><li>More later </li></ul></ul>
    10. 10. What is a “star cluster”? <ul><li>stars formed together at same time </li></ul><ul><li>stars may be gravitationally bound together </li></ul><ul><li>two types: open (galactic) and globular </li></ul>Image at http://hubblesite.org/newscenter/archive/releases/star%20cluster/globular/2007/18/image/a/format/web/results/50/
    11. 11. Open Clusters <ul><li>dozens to thousands of stars </li></ul><ul><li>young stars! only a few million years old </li></ul><ul><li>may still be surrounded by nebula from which they formed </li></ul><ul><li>located in the spiral arms of a galaxy </li></ul><ul><li>example: Pleiades </li></ul>Image at http://hubblesite.org/newscenter/archive/releases/star%20cluster/open/2004/20/image/a/results/50/
    12. 12. More open star clusters Image from http://hubblesite.org/newscenter/archive/releases/star%20cluster/open/2006/17/image/a/results/50/
    13. 13. Globular Clusters <ul><li>millions to hundreds of millions of stars </li></ul><ul><li>old! 6 to 13 billion years </li></ul><ul><li>mostly red giants and dwarfs </li></ul><ul><li>stars are clumped closely together, especially near the center of the cluster (densely) </li></ul><ul><li>surround our disk as a halo </li></ul>Image at http://hubblesite.org/newscenter/archive/releases/star%20cluster/globular/1999/26/image/a/results/50/
    14. 14. What is a “nebula”? <ul><li>A cloud in space </li></ul><ul><li>Made of gas and dust </li></ul><ul><ul><li>Can have stars inside </li></ul></ul><ul><li>Most of the ones we see are inside our Milky Way Galaxy </li></ul><ul><li>Different types </li></ul>Orion image at http://hubblesite.org/newscenter/archive/releases/2006/01/image/a/results/50/
    15. 15. Large, massive, bright nebulae <ul><li>Emission Nebula </li></ul><ul><li>The hot gas is emitting light </li></ul>Orion image at http://hubblesite.org/newscenter/archive/releases/2006/01/image/a/results/50/
    16. 16. Colder, darker nebulae Dark dust blocking the hot gas behind it NOAO/AURA/NSF Image from http://hubblesite.org/newscenter/archive/releases/nebula/dark/2001/12/image/c/results/50/
    17. 17. Leftovers from an Explosion Supernova remnant (smaller, less gas) Image at http://hubblesite.org/newscenter/archive/releases/nebula/supernova-remnant/2005/37/results/50/
    18. 18. What is a “galaxy”? <ul><li>A large group of stars outside of our own Milky Way </li></ul><ul><li>Made of billions to trillions of stars </li></ul><ul><ul><li>Also may have gas and dust </li></ul></ul><ul><li>Spiral, or elliptical, or irregular shaped </li></ul>Image at http://hubblesite.org/newscenter/archive/releases/galaxy/spiral/2007/41/results/50/
    19. 19. Spiral galaxy--Andromeda NOAO/AURA/NSF Images at http://www.noao.edu/image_gallery/html/im0606.html and http://www.noao.edu/image_gallery/html/im0685.html
    20. 20. Elliptical Galaxies Images at http://hubblesite.org/newscenter/archive/releases/galaxy/elliptical/2007/08/image/a/format/large_web/results/50/ and http://hubblesite.org/newscenter/archive/releases/galaxy/elliptical/1995/07/results/50/
    21. 21. Irregular Galaxies NASA and NOAO/AURA/NSF Images at http://hubblesite.org/newscenter/archive/releases/galaxy/irregular/2005/09/results/50/ , http://www.noao.edu/image_gallery/html/im0560.html , and http://www.noao.edu/image_gallery/html/im0993.html
    22. 22. Our Galaxy: the Milky Way <ul><li>has about 200 billion stars, and lots of gas and dust </li></ul><ul><li>is a barred-spiral (we think) </li></ul><ul><li>about 100,000 light-years wide </li></ul><ul><li>our Sun is halfway to the edge, revolving at half a million miles per hour around the center of the Galaxy </li></ul><ul><li>takes our Solar System about 200 million years to revolve once around our galaxy </li></ul>
    23. 23. The Milky Way Image at http://news.nationalgeographic.com/news/bigphotos/1945371.html
    24. 24. Mapping the Milky Way <ul><li>We can see stars </li></ul><ul><li>star clusters </li></ul><ul><li>nebulae </li></ul><ul><li>Galaxies </li></ul><ul><li>Let’s try to Map our Galaxy </li></ul>How do we know what our Galaxy looks like?
    25. 25. Measuring Distances <ul><li>Parallax (let’s model it) </li></ul><ul><ul><li>As Earth orbits the Sun, we see nearby stars move relative to more distant stars </li></ul></ul><ul><ul><li>How many degrees did the plate move, relative to the background? </li></ul></ul><ul><ul><li>Can you calculate the distance to the plate? </li></ul></ul><ul><ul><li>Sine of the parallax (angle) x Earth’s distance to the Sun = Distance to the star </li></ul></ul><ul><ul><li>The angles involved for strellar observations are very small and difficult to measure. Proxima Centauri, has a parallax of 0.77 arcsec. This angle is approximately the angle subtended by an object about 2 centimeters in diameter located about 5.3 kilometers away. </li></ul></ul>
    26. 26. Measuring Distances <ul><li>What is a Light Year? </li></ul><ul><ul><li>A light year is the distance light travels in a year. Light moves at a velocity of about 300,000 kilometers (km) each second; how far would it move in a year? </li></ul></ul><ul><ul><li>About 10 trillion km (or about 6 trillion miles). </li></ul></ul><ul><li>Why do we use light years? </li></ul><ul><ul><li>Show me how far 5 centimeters is. </li></ul></ul><ul><ul><li>Now show me 50 centimeters. </li></ul></ul><ul><ul><li>Now tell me (without thinking about it, or calculating it in meters) how far 500 centemeters is. 2000? 20,000? </li></ul></ul><ul><ul><li>We need numbers that make sense to us in relationship to objects; we scale up and use meters and kilometers for large numbers. </li></ul></ul>
    27. 27. Time for a Break! Next Up <ul><li>Our Place in the Universe </li></ul><ul><li>The Electromagnetic Spectrum </li></ul><ul><li>Classifying Stars </li></ul><ul><li>Classifying Galaxies </li></ul><ul><li>History of the Universe </li></ul>
    28. 28. Let’s check your knowledge <ul><li>Please draw an electromagnetic spectrum on a sheet of paper, and label the parts. </li></ul><ul><li>You can work in groups. </li></ul>
    29. 29. Radiation <ul><li>There are lots of types of light (radiation), including visible and invisible </li></ul>Electromagnetic spectrum http://coolcosmos.ipac.caltech.edu/cosmic_classroom/ir_tutorial/what_is_ir.html .
    30. 30. Let’s Observe A Spectrum <ul><li>What will the spectrum look like with a red filter in front of your eyes? A blue filter? </li></ul><ul><li>Hypothesize and test your hypothesis. </li></ul><ul><li>Now let’s examine the invisible parts—using our cell phones and a solar cell. </li></ul>
    31. 31. <ul><li>There are different types of spectra </li></ul><ul><ul><li>Continuous </li></ul></ul><ul><ul><li>Emission or Bright Line (from ionized gas, like a nebula or a neon sign) </li></ul></ul><ul><ul><li>Absorption or dark line (from stars) </li></ul></ul>Illustration at http://imagine.gsfc.nasa.gov/docs/science/how_l1/spectra.html
    32. 32. Radiation <ul><li>All stars emit radiation </li></ul><ul><ul><li>Radio, infrared, visible, ultraviolet, x-ray and even some gamma rays </li></ul></ul><ul><ul><li>Most sunlight is yellow-green visible light or close to it </li></ul></ul>The Sun at X-ray wavelengths Image at http://imagine.gsfc.nasa.gov/docs/science/know_l1/sun.html Image and info at http://imagine.gsfc.nasa.gov/docs/teachers/gammaraybursts/imagine/page18.html .
    33. 33. Using a Star’s Spectrum <ul><li>We can use a star’s spectrum to classify it. </li></ul>NOAO/AURA/NSF image at http://antwrp.gsfc.nasa.gov/apod/ap010530.html
    34. 34. Stellar Evolution
    35. 35. Time to Create a Stellar Graph <ul><li>Everyone will receive several “stars” </li></ul><ul><li>Place them on the large paper, according to their color and their brightness </li></ul><ul><li>This is a version of the Hertzsprung-Russell diagram. </li></ul>
    36. 36. Hertzsprung-Russell Diagram Images from http://www.nasa.gov/centers/goddard/news/topstory/2007/spectrum_plants.html and http://sunearthday.gsfc.nasa.gov/2009/TTT/65_surfacetemp.php
    37. 37. Young stars form in nebulae from Small Magellanic Cloud Image at http://hubblesite.org/newscenter/archive/releases/2007/04/image/a/results/50/
    38. 38. Star-forming region in the Large Magellanic Cloud: http://hubblesite.org/newscenter/archive/releases/2008/31/image/a/results/50/
    39. 39. Orion image at http://hubblesite.org/newscenter/archive/releases/2006/01/image/a/results/50/
    40. 40. Interstellar “eggs” Movie at http://www.stsci.edu/EPA/PR/95/44/M16.mpg
    41. 41. Our Sun is a Regular/ Small Star Image at http://www.gsfc.nasa.gov/topstory/20011210insidesun.html On the “Main Sequence”
    42. 42. In a few Billion years… Red Giant Image at http://hubblesite.org/newscenter/archive/releases/1997/26/image/a/
    43. 43. Our Sun’s Habitable Zone <ul><li>Billions of years ago, things may have been different </li></ul><ul><ul><li>The Sun was cooler (by up to 30%!) </li></ul></ul><ul><ul><li>Earth’s atmosphere was different (thicker, carbon dioxide) </li></ul></ul><ul><li>Conditions will be different in the future </li></ul><ul><ul><li>By many accounts, increases in the Sun’s temperature will make Earth uninhabitable in 1 billion years or less </li></ul></ul><ul><ul><li>These changes will also affect other planets… Mars? </li></ul></ul>Animation at http://www.nasa.gov/97994main_BHabitableZone.MPG
    44. 44. By 5 billion years… White Dwarf Image at http://hubblesite.org/newscenter/archive/releases/nebula/planetary/1998/39/results/50/ Small, but very hot
    45. 45. Image at http://hubblesite.org/newscenter/archive/releases/nebula/planetary/2000/28/image/a/format/web_print/results/50/
    46. 46. Image at http://hubblesite.org/newscenter/archive/releases/nebula/planetary/2004/27/image/a/format/large_web/results/50/
    47. 47. Massive Stars are different Image from http://hubblesite.org/newscenter/archive/releases/nebula/emission/1997/33/results/50/ On the “Main Sequence” but not for long
    48. 48. Betelgeuse—Red Supergiant Image from http://hubblesite.org/newscenter/archive/releases/star/massive%20star/1996/04/image/a/results/50/
    49. 49. Supernova—Massive Star Explodes Images at http://hubblesite.org/newscenter/archive/releases/star/supernova/2004/09/results/50/ http://hubblesite.org/newscenter/archive/releases/nebula/supernova-remnant/2005/37/results/50/ http://chandra.harvard.edu/photo/2009/casa/
    50. 50. Neutron Star or Pulsar Image at http://hubblesite.org/newscenter/archive/releases/nebula/supernova-remnant/2002/24/results/50/
    51. 51. Black Hole Image at http://hubblesite.org/newscenter/archive/releases/2002/30/image/a/results/50/
    52. 52. Classifying Galaxies
    53. 53. Galaxies <ul><li>come in different sizes (dwarf, large, giant) </li></ul><ul><li>come in different shapes and classifications </li></ul><ul><ul><li>Spirals </li></ul></ul><ul><ul><li>Ellipticals </li></ul></ul><ul><ul><li>Lenticulars </li></ul></ul><ul><ul><li>Irregulars </li></ul></ul><ul><li>are fairly close together, relative to their sizes </li></ul>
    54. 54. Spiral Galaxies <ul><li>have flat disk, spiral arms, central bulge, and a surrounding halo </li></ul><ul><li>some have a “barred” bulge </li></ul><ul><li>are fairly large (no dwarf spirals) </li></ul><ul><li>have lots of gas and dust and younger stars in their arms, but older stars and little gas or dust in their halos and central bulges </li></ul>
    55. 55. Galaxies Image at http://hubblesite.org/newscenter/archive/releases/galaxy/spiral/2005/01/results/50/
    56. 56. Spiral galaxy--Andromeda NOAO/AURA/NSF Images at http://www.noao.edu/image_gallery/html/im0606.html and http://www.noao.edu/image_gallery/html/im0685.html
    57. 57. Spiral Galaxy on Edge Image at http://hubblesite.org/newscenter/archive/releases/galaxy/spiral/2006/24/image/a/results/50/
    58. 58. Image at http://hubblesite.org/newscenter/archive/releases/galaxy/spiral/2007/41/results/50/
    59. 59. Elliptical galaxies <ul><li>range from spherical to football shaped </li></ul><ul><li>range from very small to giant </li></ul><ul><li>have very little gas or dust </li></ul><ul><li>mostly old stars </li></ul><ul><li>similar to the central bulge of a spiral galaxy </li></ul>
    60. 60. Elliptical Galaxies Images at http://hubblesite.org/newscenter/archive/releases/galaxy/elliptical/2007/08/image/a/format/large_web/results/50/ and http://hubblesite.org/newscenter/archive/releases/galaxy/elliptical/1995/07/results/50/
    61. 61. Lenticular <ul><li>have a disk but no arms </li></ul><ul><li>have little or no excess gas and dust </li></ul>Image at http://hubblesite.org/newscenter/archive/releases/galaxy/elliptical/2002/07/results/50/
    62. 62. Irregular Galaxies <ul><li>any galaxy that isn’t a Spiral, Elliptical, or Lenticular </li></ul><ul><li>usually have lots of gas and dust and young stars </li></ul><ul><li>may have a distorted shape from interaction with another galaxy </li></ul>
    63. 63. Irregular Galaxies NASA and NOAO/AURA/NSF Images at http://hubblesite.org/newscenter/archive/releases/galaxy/irregular/2005/09/results/50/ , http://www.noao.edu/image_gallery/html/im0560.html , and http://www.noao.edu/image_gallery/html/im0993.html
    64. 64. Collisions! <ul><li>We now think that galaxies in groups and clusters often collide </li></ul><ul><li>The Milky Way is moving at 300,000 mph toward the Andromeda Galaxy </li></ul><ul><li>They may collide in about 5 billion years </li></ul><ul><li>Stars don’t usually collide </li></ul><ul><li>New orbits, gas piles up to form new stars </li></ul>
    65. 65. Interacting Image from http://hubblesite.org/newscenter/archive/releases/galaxy/interacting/2000/34/results/50/
    66. 66. the Antennae or Mice Information at http://hubblesite.org/newscenter/archive/releases/galaxy/interacting/1997/34/results/50/
    67. 67. Images from http://hubblesite.org/newscenter/archive/releases/galaxy/spiral/2002/21/image/a/results/50/ and http://hubblesite.org/newscenter/archive/releases/galaxy/spiral/1999/16/image/a/results/50/ The occasional results of two galaxies colliding: ringed galaxies
    68. 68. Various galaxies (can you identify types?) Image at http://hubblesite.org/newscenter/archive/releases/galaxy/cluster/1999/31/results/50/
    69. 69. Supermassive black holes <ul><li>almost every medium to large galaxy we’ve check has a supermassive black hole at the center </li></ul><ul><li>the larger the galaxy, the more massive the black hole </li></ul><ul><li>we don’t know which comes first, the galaxy or the black hole </li></ul><ul><li>we think that these black holes are responsible for some of the galaxies with jets and lobes which give off radio waves, x-rays, etc. </li></ul>
    70. 70. Active galaxy Image at http://hubblesite.org/newscenter/archive/releases/galaxy/spiral/2000/37/results/50/
    71. 71. at the center of a large galaxy Image at http://hubblesite.org/newscenter/archive/releases/exotic/black-hole/1998/22/results/20/ and http://hubblesite.org/newscenter/archive/releases/exotic/black%20hole/2000/21/image/a/format/web_print/results/20/
    72. 72. Galaxy Clusters <ul><li>the Local Group </li></ul><ul><ul><li>includes the Milky Way, the Andromeda, and over 30 other smaller galaxies </li></ul></ul><ul><li>the Virgo Cluster </li></ul><ul><ul><li>hundreds to thousands of galaxies, 60 million light-years away </li></ul></ul><ul><ul><li>giant elliptical at center, formed by galactic cannibalism </li></ul></ul><ul><ul><li>the Local Group is “falling” toward the Virgo Cluster at 60 to 250 miles per second! </li></ul></ul>
    73. 73. Coma Cluster Image at http://hubblesite.org/newscenter/archive/releases/galaxy/cluster/2008/24/image/a/results/20/
    74. 74. Superclusters! <ul><li>clusters are bound together in larger structures, called superclusters </li></ul><ul><li>these superclusters have been mapped, and are grouped into long strings </li></ul><ul><ul><li>300 million to a billion light-years long </li></ul></ul><ul><ul><li>100 to 300 million light-years wide </li></ul></ul><ul><ul><li>and only 10 to 30 million light-years thick </li></ul></ul><ul><li>in between these strings are huge voids of galaxies, although some astronomers may have detected hot gas </li></ul>
    75. 75. Evolution of Galaxies Image at http://www.galex.caltech.edu/media/glx2007-05f_img01.html
    76. 76. Origin of the Universe <ul><li>Big Bang </li></ul><ul><ul><li>Dominant scientific theory about the origin of the universe </li></ul></ul><ul><ul><li>Occurred ~13.7 billion years ago </li></ul></ul><ul><li>What is the Big Bang? </li></ul><ul><li>How do we know? </li></ul>
    77. 77. What is the Big Bang? <ul><li>Infinitely dense point not governed by our physical laws or time </li></ul><ul><li>All matter and energy contained in one point </li></ul>Image from http://www.newscientist.com/articleimages/dn11799/0-did-antimatter-factory-spark-brightest-supernova.html
    78. 78. Building a Universe <ul><li>Instantaneous filling of space with all matter </li></ul>
    79. 79. History of the Universe <ul><li>10 -43 seconds - gravity separates from other forces </li></ul><ul><li>10 -35 to 10 -32 seconds - fundamental particles - quarks and electrons </li></ul><ul><li>10 -6 seconds - quarks combine into protons and neutrons </li></ul><ul><li>1 second - electromagnetic and weak nuclear forces separate </li></ul><ul><li>3 minutes - protons and neutrons combine into atomic nuclei </li></ul><ul><li>10 5 years - electrons join nuclei to make atoms; light is emitted </li></ul><ul><li>10 5 -10 9 years - matter collapses into clouds, making galaxies and stars </li></ul>Orion Nebula - http://stardate.utexas.edu/resources/ssguide/planet_form.html
    80. 80. History of the Universe Image from http://dsc.discovery.com/space/top-10/strange-universe/space-10-weirdest-things-universe-10.html
    81. 81. Later History Image at http://www.galex.caltech.edu/media/glx2004-01r_img02.html
    82. 82. Big Bang Theory <ul><li>In 1915, Albert Einstein concluded that the universe could not be static based on his recently-discovered theory of relativity and a dded a &quot;cosmological constant&quot; to the theory of relativity because astronomers assured him that the universe was static </li></ul><ul><li>Aleksandr Friedmann and Abbe George LeMaitre are credited with developing the basics of the Big Bang model between 1922 and 1927; their calculations suggested that universe is expanding , not static. </li></ul><ul><li>Years later, Einstein called his cosmological constant the biggest mistake of his career </li></ul>Image at http://map.gsfc.nasa.gov/universe/bb_theory.html
    83. 83. Expanding Universe <ul><li>In 1929, Edwin Hubble showed that most galaxies are red-shifted (moving away from us), and that a galaxy’s velocity is proportional to its distance (galaxies that are twice as far from us move twice as fast) </li></ul>Image from http://imagine.gsfc.nasa.gov/docs/science/mysteries_l1/origin_destiny.html
    84. 84. Hubble’s Evidence <ul><li>Doppler shifting - wavelength emitted by something moving away from us is shifted to a lower frequency </li></ul><ul><li>Sound of a fire truck siren - pitch of the siren is higher as the fire truck moves towards you, and lower as it moves away from you </li></ul><ul><li>Visible wavelengths emitted by objects moving away from us are shifted towards the red part of the visible spectrum </li></ul><ul><li>The faster they move away from us, the more they are redshifted. Thus, redshift is a reasonable way to measure the speed of an object. </li></ul><ul><li>When we observe the redshift of galaxies, almost every galaxy appears to be moving away from us – the Universe is expanding. </li></ul>
    85. 85. Predictions for the Big Bang Model <ul><li>The expansion of the Universe </li></ul><ul><ul><li>Edwin Hubble's 1929 observation that galaxies were generally receding from us provided the first clue that the Big Bang theory might be right. </li></ul></ul><ul><li>The abundance of the light elements H, He, Li </li></ul><ul><ul><li>The Big Bang theory predicts that these light elements should have been fused from protons and neutrons in the first few minutes after the Big Bang. </li></ul></ul><ul><li>The cosmic microwave background (CMB) radiation </li></ul><ul><ul><li>The early universe should have been very hot. The cosmic microwave background radiation is the remnant heat leftover from the Big Bang. </li></ul></ul>
    86. 86. Evidence for Big Bang <ul><li>Red shift - as light from distant galaxies approach earth there is an increase of space between earth and the galaxy, which leads to wavelengths being stretched </li></ul><ul><li>In 1964, Arno Penzias and Robert Wilson, discovered a noise of extraterrestrial origin that came from all directions at once - radiation left over from the Big Bang </li></ul><ul><li>In June 1995, scientists detected helium in the far reaches of the universe - consistent with an important aspect of the Big Bang theory that a mixture of hydrogen (75%) and helium (25%) was created at the beginning of the universe </li></ul>
    87. 87. When Did the Universe Form? <ul><li>~13.7 billion years ago </li></ul><ul><li>How do we know? </li></ul><ul><ul><li>Spreading (Red Shift) - know distances, rates of retreat, relative positions </li></ul></ul><ul><ul><li>Pervasive background radiation of 2.7°C above absolute zero - afterglow of the Big Bang </li></ul></ul>http://timeline.aps.org/APS/resources/85_06a.jpg Cosmic background radiation temperature on celestial sphere
    88. 88. Feedback, Questions <ul><li>Reach us online at http://www.lpi.usra.edu/education/ </li></ul><ul><li>For more information, contact </li></ul><ul><li>Christine Shupla Lunar and Planetary Institute 3600 Bay Area Blvd Houston, TX  77058 (281) 486-2135 [email_address] </li></ul>

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